These are just two examples of how much we have yet to learn about our planet. As for the plants and animals that share our home, a recent study -- "How Many Species Are There on Earth and in the Ocean?" -- suggests that of the estimated 8.7 million species on Earth, 86 per cent on land and 91 per cent in the oceans have not been described by scientists. And describing just means identifying and naming. It doesn't mean we know anything about population numbers, geographic distribution, what they eat, how they reproduce, or their relationship with other species.

Authors of the study, published in the scientific journal PLoS Biology, argue that understanding the range of biodiversity in our world is crucial to conservation. In many cases, plants and animals are going extinct before we even know of their existence. "We know we are losing species because of human activity, but we can't really appreciate the magnitude of species lost until we know what species are there," study co-author Camilo Mora said.

As well as the titi monkey, other animals recently discovered include a small African antelope, a bacterium that consumes iron-oxide on the sunken Titanic, an underwater mushroom, a jumping cockroach, and a "prehistoric" eel found in a cave in the Pacific Ocean. The eel has so many unusual features, including a second upper jaw, that it has been classified as a new species belonging to a new genus and family.

And, several species that were thought to have been extinct have since been rediscovered. However, researchers say this doesn't mean they have recovered. Pretty much all of them are still at risk of extinction. In fact, 92 per cent of all amphibians and 86 per cent of all birds and mammals are believed to be facing extinction, and tens of thousands of species are being wiped out every year.

Many factors are at play in this biodiversity crisis, but most are related to human activity. Habitat destruction and conversion of land for agriculture and development are big ones. The spread of invasive species, overexploitation of natural resources, pollution, and climate change are also major contributors to what some scientists are calling the sixth great extinction.

Unlike the previous mass extinctions, this one is human-caused. But the history of these extinctions should also tell us something. Nature and the planet are resilient. They bounce back after major crises, but -- and this is crucial -- not until the cause of the extinction or crisis has dissipated. This means we humans are putting ourselves on a path to extinction. The way out is to recognize that we are a part of the natural world and not something that stands outside of it. We absolutely depend on all that nature provides for our existence.

Bringing about necessary changes won't be easy. It will require stabilizing and reducing global population, reevaluating our economic systems to reduce the pressures of consumerism, addressing climate change and pollution, protecting large swaths of terrestrial, marine, and freshwater habitat, and learning more about the natural world. Conservation efforts are essential. These will help plants and animals become more resilient to climate change, but they can also help slow climate change. For example, forests absorb and store carbon, so protecting them not only helps the plants and animals that live in them, it also helps reduce the amount of carbon dioxide in the atmosphere.

Of course, as the species study makes clear, we must address the massive knowledge gaps about our world. Unfortunately, economic pressures, antipathy toward science, and the fact that we often spend more money to learn about other planets than our own mean that we have a long way to go to avoid catastrophe.

We can't and needn't give up hope, though. Thanks to the work of scientists and other thinkers, we learn more about our world every day. Above all, we really need to learn how crucial this knowledge is to our future.

Dr. David Suzuki is a scientist, broadcaster, author, and co-founder of the David Suzuki Foundation. Written with contributions from David Suzuki Foundation editorial and communications specialist Ian Hanington.